An optical fiber preform is a cylindrical glass body from which optical fiber is made by a process known as drawing. As is described, for example, in the patent of Glantschnig et al., U.S. Pat. No. 4,934,818, granted Jun. 19, 1990, prior to drawing, it is normally necessary to determine the optical characteristics of the preform by directing a narrow monochromatic beam of light through the preform. During this testing operation, the preform is customarily submerged in a container of oil known as index-matching oil that has a refractive index that matches that of the preform.
After the optical test, the index-matching oil must be cleaned from the preform. This is a particularly crucial step if a hollow cylindrical jacket of glass is to be fitted over the preform to expand its diameter prior to drawing. The cleaning process may include detergent cleaning, followed by a water rinse. Cleaned preforms are then finally dried in hot nitrogen. The cleaning process typically takes approximately sixty minutes and generates liquid waste, which, since it includes oil and detergent, is potentially environmentally hazardous. It would be desirable to reduce the time needed for cleaning, and to reduce or eliminate liquid waste associated with cleaning. It would also be desirable if one could recycle the index-matching oil cleaned from each preform.